A number of experiments are being conducted to explore the axion DM, and various limits have been placed on its interactions with the SM particles. In particular, axions coupled to photons are often referred to as axion-like particles (ALPs). Light axions are easily produced in hot stellar interiors, which affects stellar evolution by carrying energy outside the star. For instance, the interaction between the axion and photons is restricted by horizontal branch stars [1]}, and the interaction between the axion and electrons is restricted by observations of the tip of red giant branch [2]}, [3]} and white dwarfs [4]}, [5]}, [6]}. It is also known that when the axion mass exceeds \({\cal O}(10)\)  eV, the observational limit on the photon flux produced by axion decay becomes very tight. Assuming the anomalous coupling with photons, the decay constant of the axion of keV-scale mass must be above the GUT scale. Such axion DM with the GUT-scale decay constant is far beyond the sensitivity expected in current and near-future direct search experiments, and its contribution to the stellar cooling process is negligibly small.
